Golf ball covers made from polyureas based on polycaprolactones

ABSTRACT

A golf ball having a cover material made from a polyurea composition is provided. In one version, the golf ball includes a polybutadiene core and surrounding cover layer made of a polyurea composition. In another version, the golf ball includes a polybutadiene core, an intermediate casing layer made of ionomer resin, and an outer cover layer made of the polyurea composition. The polyurea composition is the reaction product of an isocyanate, amine-terminated polycaprolactone, and amine-terminated curing agent. The resulting cover material has many advantageous properties including improved durability, toughness, abrasion-resistance, and moisture-resistance.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to a golf ball having a covermaterial made from a polyurea composition. More particularly, thepolyurea composition is the reaction product of an isocyanate,amine-terminated polycaprolactone, and amine-terminated curing agent.The resulting cover material has many advantages including improveddurability, toughness, abrasion-resistance, and moisture-resistance.

2. Brief Review of the Related Art

In recent years, manufacturers of golf balls have expanded theirresearch efforts to develop golf ball cover materials having moredesirable properties and performance characteristics. In particular, thegolf industry has looked to develop cover materials having improved“hard” properties while maintaining optimum “soft” properties. Improveddurability, toughness, and abrasion-resistance are some of the desiredhard properties. The soft properties provide the player with a better“feel” when he/she strikes the ball with a golf club. The player sensesmore control over the ball as the club face makes impact. The hardproperties of the ball help players achieve greater flight distance withtheir shots. While the softer feel of the ball cover allows players toplace a spin on the ball and better control its flight pattern.

In the past, natural or synthetic rubber covered golf balls werecommonly used. For example, balata covered balls were once very popular,because they provided good flight distance with a soft feel. Golfplayers experienced a pleasant sensation when striking the relativelysoft balata ball and were able to better control the ball's flightpattern. The players could hear a “clicking” sound as the club facestruck the ball. One disadvantage with using such balata covered balls,however, was the covers tended to wear away after repeated play. Thebalata balls generally did not have high durability,cut/shear-resistance, or impact-resistance. In turn, the golf industrylooked to ionomer resins to make more durable covers. These cross-linkedpolymers contain interchain ionic bonding as well as covalent bonding.The ionomer resins include, for example, a copolymer of ethylene and avinyl comonomer with an acid group such as methacrylic or acrylic acid.Metal ions such as sodium, lithium, zinc, and magnesium are used toneutralize the acid groups in the polymer. Commercially availableionomer resins are known in the industry and include numerous resinssold under the trademarks, Surlyn® (DuPont) and Escor® and Iotek®(Exxon). The ionomer resins are available in various grades and areidentified based on the type of base resin, molecular weight, type ofmetal ion, amount of acid, degree of neutralization, additives, andother properties. Ball covers made with such ionomer resins showexcellent, durability, mechanical strength, and cut/shear-resistance.However, at the same time, these ball covers have a hard surface andplayers may experience a loss in feel and comfort when making shots withthese balls.

More recently, the golf industry has looked at making golf ball coversfrom polyurea compositions. For example, Wu, U.S. Pat. No. 5,484,870discloses a polyurea composition suitable for molding golf ball covers.The polyurea composition is the reaction product of an organic compoundhaving at least two isocyanate functional groups and an amine curingagent. The mole equivalent ratio of amine groups to isocyanate groupsmay vary over a wide range. Additional materials such as colorants,ultraviolet light absorbers, plasticizers, and the like may be includedin the compositions.

Bulpett et al., U.S. Pat. No. 6,964,621 discloses polyurea compositionsthat can be used in the construction of golf balls. The compositions areprepared from a polyurea prepolymer and a curing agent. According to the'621 patent, the resulting golf ball has improved cut and shearresistance.

Although some conventional polyurea cover materials have been somewhateffective, there is still a need for improved golf ball coverings.Particularly, it would be desirable to have a polyurea cover materialthat could provide enhanced durability, toughness, andabrasion-resistance to the golf ball but without sacrificing playingperformance properties such as feel, softness, spin control, and thelike. The present invention provides such golf balls. It also would bedesirable to have a cover material that showed high weather andmoisture-resistance. Such a ball covering would prevent the ball fromgaining water and increasing in size and weight. The present inventionprovides such a ball covering having these properties as well as otheradvantageous features and benefits.

SUMMARY OF THE INVENTION

The present invention provides a golf ball having a cover material madefrom a polyurea composition, which is the reaction product of anisocyanate, amine-terminated polycaprolactone, and amine-terminatedcuring agent. The resulting polyurea cover material has many advantagesincluding improved durability, toughness, abrasion-resistance, andmoisture-resistance. In one version, the golf ball includes apolybutadiene core and surrounding cover layer made of the polyureacomposition. In another version, the golf ball includes a polybutadienecore, an intermediate casing layer made of an ionomer resin, and anouter cover layer made of the polyurea composition.

Golf balls made in accordance with this invention may have variousconstructions. In one embodiment, the golf ball core has a diameter ofabout 1.26 to about 1.60 inches; the intermediate layer has a thicknessof about 0.015 to about 0.120 inches; and the cover has a thickness ofabout 0.015 to about 0.090 inches. The components constituting the golfball may be of different hardness levels. For example, in one version,the golf ball core has a hardness in the range of about 35 to about 60Shore D; the intermediate layer has a hardness in the range of about 30to about 75 Shore D, and the cover has a material hardness of about 30to about 65 Shore D.

BRIEF DESCRIPTION OF THE DRAWINGS

The novel features that are characteristic of the present invention areset forth in the appended claims. However, the preferred embodiments ofthe invention, together with further objects and attendant advantages,are best understood by reference to the following detailed descriptionin connection with the accompanying drawings in which:

FIG. 1 is a cross-sectional view of a single-layered, two-piece golfball made in accordance with the present invention;

FIG. 2 is a cross-sectional view of a multi-layered, three-piece golfball made in accordance with the present invention; and

FIG. 3 is a cross-sectional view of a multi-layered, four-piece golfball including a two-piece core made in accordance with the presentinvention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention relates to golf balls having a cover material madefrom a polyurea composition. In general, polyurea compositions containurea linkages formed by reacting an isocyanate group with an aminegroup. The chain length of the polyurea is extended by reacting thepolymer with an amine-terminated curing agent. The resulting polyureahas elastomeric properties, because of its “hard” and “soft” segments,which are covalently bonded together. The soft, amorphous, low-meltingpoint segments, formed from the polyamines, are relatively flexible andmobile, while the hard, high-melting point segments, formed from theisocyanate and chain extenders, are relatively stiff and immobile. Thephase separation of the hard and soft segments provides the polymer withits elastomeric resiliency. When amine-terminated compounds are used asthe curing agent, the resulting polymer only contains urea linkages.

However, if a hydroxyl-terminated curing agent is used, any excessisocyanate groups in the polymer will react with the hydroxyl groups inthe curing agent and create urethane linkages. That is, apolyurea/urethane hybrid composition is produced, which is distinct froma pure polyurea composition. It also should be understood thatpolyurethanes and polyureas are significantly different materials.Polyurethanes contain urethane linkages formed by reacting an isocyanategroup with a hydroxyl group. Commercial polyurethane materials areproduced by the reaction of an isocyanate with a polyalcohol (polyol) inthe presence of a catalyst and other additives. The chain length of thepolyurethane is extended by reacting the polymer with a hydroxyl oramine-terminated curing agent.

Any suitable isocyanate known in the art can be used to produce thepolyurea compositions in accordance with this invention. Suchisocyanates include, for example, aliphatic, cycloaliphatic, aromaticaliphatic, aromatic, any derivatives thereof, and combinations of thesecompounds having two or more isocyanate (—N═C═O) groups per molecule.The isocyanates may be organic polyisocyanate-terminated prepolymers,low free isocyanate prepolymers, and mixtures thereof. Theisocyanate-containing reactable component may also include anyisocyanate-functional monomer, dimer, trimer, or polymeric adductthereof, prepolymer, quasi-prepolymer, or mixtures thereof.Isocyanate-functional compounds may include monoisocyanates orpolyisocyanates that include any isocyanate functionality of two ormore.

Preferred isocyanates include diisocyanates (having two NCO groups permolecule), biurets thereof, dimerized uretdiones thereof, trimerizedisocyanurates thereof, and polyfunctional isocyanates such as monomerictriisocyanates. Diisocyanates typically have the generic structure ofOCN—R—NCO. Exemplary diisocyanates include, but are not limited to,unsaturated isocyanates such as: p-phenylene diisocyanate (“PPDI,” i.e.,1,4-phenylene diisocyanate), m-phenylene diisocyanate (“MPDI,” i.e.,1,3-phenylene diisocyanate), o-phenylene diisocyanate (i.e.,1,2-phenylene diisocyanate), 4-chloro-1,3-phenylene diisocyanate,toluene diisocyanate (“TDI”), m-tetramethylxylene diisocyanate(“m-TMXDI”), p-tetramethylxylene diisocyanate (“p-TMXDI”), 1,2-, 1,3-,and 1,4-xylene diisocyanates, 2,2′-, 2,4′-, and 4,4′-biphenylenediisocyanates, 3,3′-dimethyl-4,4′-biphenylene diisocyanate (“TODI”),2,2′-, 2,4′-, and 4,4′-diphenylmethane diisocyanates (“MDI”),3,3′-dimethyl-4,4′-diphenylmethane diisocyanate, carbodiimide-modifiedMDI, polyphenylene polymethylene polyisocyanate (“PMDI,” i.e., polymericMDI), 1,5-naphthalene diisocyanate (“NDI”), 1,5-tetrahydronaphththalenediisocyanate, anthracene diisocyanate, tetracene diisocyanate; andsaturated isocyanates such as: 1,4-tetramethylene diisocyanate,1,5-pentamethylene diisocyanate, 2-methyl-1,5-pentamethylenediisocyanate, 1,6-hexamethylene diisocyanate (“HDI”) and isomersthereof, 2,2,4- and 2,4,4-trimethylhexamethylene diisocyanates,1,7-heptamethylene diisocyanate and isomers thereof, 1,8-octamethylenediisocyanate and isomers thereof, 1,9-novamethylene diisocyanate andisomers thereof, 1,10-decamethylene diisocyanate and isomers thereof,1,12-dodecane diisocyanate and isomer thereof, 1,3-cyclobutanediisocyanate, 1,2-, 1,3-, and 1,4-cyclohexane diisocyanates, 2,4- and2,6-methylcyclohexane diisocyanates (“HTDI”), isophorone diisocyanate(“IPDI”), isocyanatomethylcyclohexane isocyanate,isocyanatoethylcyclohexane isocyanate, bis(isocyanatomethyl)cyclohexane(i.e., 1,4-cyclohexane-bis(methylene isocyanate)),4,4′-dicyclohexylmethane diisocyanate (“H₁₂ MDI,” i.e.,bis(4-isocyanatocyclohexyl)-methane), 2,4′- and 4,4′-dicyclohexanediisocyanates, 2,4′- and 4,4′-bis(isocyanatomethyl) dicyclohexanes.Dimerized uretdiones of diisocyanates and polyisocyanates include, forexample, unsaturated isocyanates such as uretdiones of toluenediisocyanates, uretdiones of diphenylmethane diisocyanates; andsaturated isocyanates such as uretdiones of hexamethylene diisocyanates.Trimerized isocyanurates of diisocyanates and polyisocyanates include,for example, unsaturated isocyanates such as trimers of diphenylmethanediisocyanate, trimers of tetramethylxylene diisocyanate, isocyanuratesof toluene diisocyanates; and saturated isocyanates such asisocyanurates of isophorone diisocyanate, isocyanurates of hexamethylenediisocyanate, isocyanurates of trimethyl hexamethylene diisocyanates.Monomeric triisocyanates include, for example, unsaturated isocyanatessuch as 2,4,4′-diphenylene triisocyanate, 2,4,4′-diphenylmethanetriisocyanate, 4,4′,4″-triphenylmethane triisocyanate; and saturatedisocyanates such as: 1,3,5-cyclohexane triisocyanate. Preferably, theisocyanate is selected from the group consisting of MDI, H₁₂MDI, PPDI,TDI, IPDI, HDI, NDI, XDI, TMXDI, THDI, and TMDI, and homopolymers andcopolymers and mixtures thereof.

As discussed above, polyurea is an elastomeric material that is thereaction product of an isocyanate component and amine-terminated polymerresin. As described further below, of the many possible amine-terminatedcompounds that can be used in the reaction process, it was found thatamine-terminated polycaprolactones can be reacted with the isocyanate toprovide a polyurea composition having the most desirable properties forpurposes of this invention. In general, caprolactone is a cyclic estercompound having the following generic structure:

Methods for making amine-terminated polycaprolactone compounds are knownin the art and described in such references as Carr et al., (Solvay)published PCT International Application WO 2006/040355 A1, thedisclosure of which is hereby incorporated by reference. In the methoddescribed in the '355 PCT Publication, the lactone ring is opened usinga polycarboxylic acid initiator to produce a polycaprolactone polymerhaving carboxylic acid groups located at its terminal ends. In turn,this product is reacted with a polyamine at a temperature above 50° C.to produce an amine-terminated polycaprolactone polymer having thefollowing generic structure:

The molecular weight of the amine-terminated polycaprolactone isgenerally in the range of about 1000 to about 10,000.

It has been found that the amine-terminated polycaprolactones of thisinvention can be reacted with isocyanates to produce polyureas havinghigh mechanical strength and integrity. Moreover, the amine-terminatedpolycaprolactones have enhanced hydrolytic stability, and it is believedthis contributes to the resulting polyurea composition having enhancedmoisture-resistance. There are less ester linkages along the carbonchain of the amine-terminated polycaprolactone and consequently lessmoisture attack sites. Furthermore, the distance between respectiveester linkages is relatively long and this helps improve hydrolyticstability. Moisture is prevented from attacking the ester linkages andbreaking-up the polymer chain into smaller, weaker chains. Thus, thepolymers have good weather resistance. The polymers show high resistanceto the effects of water and heat exposure as well as enhancedultraviolet (UV) light-stability.

There are two basic techniques that can be used to make the polyureaelastomers of this invention: a) one-shot technique, and b) prepolymertechnique. In the one-shot technique, the isocyanate, amine-terminatedcompound, and amine-terminated curing agent are reacted in one step.Meanwhile, the prepolymer technique involves a first reaction betweenthe isocyanate and amine-terminated compound to produce a polyureaprepolymer, and a subsequent reaction between the prepolymer andamine-terminated curing agent. As a result of the reaction between theisocyanate and amine-terminated polycaprolactone, there will be someunreacted NCO groups in the polyurea prepolymer. The prepolymer shouldhave less than 14% unreacted NCO groups. Preferably, the prepolymer hasno greater than 8.5% unreacted NCO groups, more preferably from 2.5% to8% and most preferably from 5.0% to 8.0% unreacted NCO groups. As theweight percent of unreacted isocyanate groups increases, the hardness ofthe composition also generally increases. Either the one-shot orprepolymer method may be employed to produce the polyurea compositionsof the invention; however, the prepolymer technique is preferred becauseit provides better control of the chemical reaction. The prepolymermethod provides a more homogeneous mixture resulting in a moreconsistent polymer composition. The one-shot method results in a mixturethat is inhomogeneous (more random) and affords the manufacturer lesscontrol over the molecular structure of the resultant composition.

In the casting process, the polyurea composition can be formed bychain-extending the polyurea prepolymer with a single curing agent or ablend of curing agents as described further below. The compositions ofthe present invention may be selected from among both castablethermoplastic and thermoset materials. Thermoplastic polyureacompositions are typically formed by reacting the isocyanate andamine-terminated compound, each having two (or less) functional groups,at a 1:1 stoichiometric ratio. For example, a prepolymer may be curedwith a secondary diamine to make the non-cross-linked thermoplasticcomposition. Thermoset compositions, on the other hand, are cross-linkedpolymers and are typically produced from the reaction of an isocyanateand amine-terminated compound, wherein each component has two (orgreater) functional groups, at normally a 1.05:1 stoichiometric ratio.For example, a prepolymer may be cured with a primary or secondarydiamine to make the cross-linked thermoset polyureas. In general,thermoset polyurea compositions are easier to prepare than thermoplasticpolyureas.

In a preferred embodiment, a pure polyurea composition is prepared. Thatis, the composition contains only urea linkages. An amine-terminatedcuring agent is used in the reaction to produce the pure polyureacomposition. However, it should be understood that a polyurea/urethanehybrid composition may be prepared in accordance with this invention insome instances. Such a hybrid composition could be obtained if thepolyurea prepolymer were cured with a hydroxyl-terminated curing agent.Any excess isocyanate in the polyurea prepolymer reacts with thehydroxyl groups in the curing agent and forms urethane linkages. Theresulting polyurea/urethane hybrid composition contains both urea andurethane linkages.

Suitable amine-terminated curing agents that can be used inchain-extending the polyurea prepolymer of this invention include, butare not limited to, unsaturated diamines such as4,4′-diamino-diphenylmethane (i.e., 4,4′-methylene-dianiline or “MDA”),m-phenylenediamine, p-phenylenediamine, 1,2- or1,4-bis(sec-butylamino)benzene, 3,5-diethyl-(2,4- or 2,6-)toluenediamine or “DETDA”, 3,5-dimethylthio-(2,4- or2,6-)toluenediamine, 3,5-diethylthio-(2,4- or 2,6-)toluenediamine,3,3′-dimethyl-4,4′-diamino-diphenylmethane,3,3′-diethyl-5,5′-dimethyl-4,4′-diamino-diphenylmethane (i.e.,4,4′-methylene-bis(2-ethyl-6-methyl-benezeneamine)),3,3′-dichloro-4,4′-diamino-diphenylmethane (i.e.,4,4′-methylene-bis(2-chloroaniline) or “MOCA”),3,3′,5,5′-tetraethyl-4,4′-diamino-diphenylmethane (i.e.,4,4′-methylene-bis(2,6-diethylaniline),2,2′-dichloro-3,3′,5,5′-tetraethyl-4,4′-diamino-diphenylmethane (i.e.,4,4′-methylene-bis(3-chloro-2,6-diethyleneaniline) or “MCDEA”),3,3′-diethyl-5,5′-dichloro-4,4′-diamino-diphenylmethane, or “MDEA”),3,3′-dichloro-2,2′,6,6′-tetraethyl-4,4′-diamino-diphenylmethane,3,3′-dichloro-4,4′-diamino-diphenylmethane,4,4′-methylene-bis(2,3-dichloroaniline) (i.e.,2,2′,3,3′-tetrachloro-4,4′-diamino-diphenylmethane or “MDCA”),4,4′-bis(sec-butylamino)-diphenylmethane,N,N′-dialkylamino-diphenylmethane,trimethyleneglycol-di(p-aminobenzoate),polyethyleneglycol-di(p-aminobenzoate),polytetramethyleneglycol-di(p-aminobenzoate); saturated diamines such asethylene diamine, 1,3-propylene diamine, 2-methyl-pentamethylenediamine, hexamethylene diamine, 2,2,4- and 2,4,4-trimethyl-1,6-hexanediamine, imino-bis(propylamine), imido-bis(propylamine),methylimino-bis(propylamine) (i.e.,N-(3-aminopropyl)-N-methyl-1,3-propanediamine),1,4-bis(3-aminopropoxy)butane (i.e.,3,3′-[1,4-butanediylbis-(oxy)bis]-1-propanamine),diethyleneglycol-bis(propylamine) (i.e.,diethyleneglycol-di(aminopropyl)ether),4,7,10-trioxamidecane-1,13-diamine, 1-methyl-2,6-diamino-cyclohexane,1,4-diamino-cyclohexane, poly(oxyethylene-oxypropylene) diamines, 1,3-or 1,4-bis(methylamino)-cyclohexane, isophorone diamine, 1,2- or1,4-bis(sec-butylamino)-cyclohexane, N,N′-diisopropyl-isophoronediamine, 4,4′-diamino-dicyclohexylmethane,3,3′-dimethyl-4,4′-diamino-dicyclohexylmethane,3,3′-dichloro-4,4′-diamino-dicyclohexylmethane,N,N′-dialkylamino-dicyclohexylmethane, polyoxyethylene diamines,3,3′-diethyl-5,5′-dimethyl-4,4′-diamino-dicyclohexylmethane,polyoxypropylene diamines,3,3′-diethyl-5,5′-dichloro-4,4′-diamino-dicyclohexylmethane,polytetramethylene ether diamines,3,3′,5,5′-tetraethyl-4,4′-diamino-dicyclohexylmethane (i.e.,4,4′-methylene-bis(2,6-diethylaminocyclohexane)),3,3′-dichloro-4,4′-diamino-dicyclohexylmethane,2,2′-dichloro-3,3′,5,5′-tetraethyl-4,4′-diamino-dicyclohexylmethane,(ethylene oxide)-capped polyoxypropylene ether diamines,2,2′,3,3′-tetrachloro-4,4′-diamino-dicyclohexylmethane,4,4′-bis(sec-butylamino)-dicyclohexylmethane; triamines such asdiethylene triamine, dipropylene triamine, (propylene oxide)-basedtriamines (i.e., polyoxypropylene triamines),N-(2-aminoethyl)-1,3-propylenediamine (i.e., N₃-amine),trimethylolpropane-based triamines, glycerin-based triamines, (allsaturated); tetramines such as N,N′-bis(3-aminopropyl)ethylene diamine(i.e., N₄-amine) (both saturated), triethylene tetramine; and otherpolyamines such as tetraethylene pentamine (also saturated). It is alsorecognized that the amine-terminated polycaprolactone material of thisinvention can be used as the amine curing agent in some instances.

As discussed above, in some instances, it may be desirable to form apolyurea/polyurethane hybrid composition. In such circumstances, thecuring agent used in the reaction of the polyurea prepolymer may beselected from the group consisting of hydroxy-terminated curing agentsand mixtures of amine-terminated and hydroxyl-terminated curing agents.

The hydroxy-terminated curing agents are preferably selected from thegroup consisting of ethylene glycol; diethylene glycol; polyethyleneglycol; propylene glycol; 2-methyl-1,3-propanediol;2-methyl-1,4-butanediol; monoethanolamine; diethanolamine;triethanolamine; monoisopropanolamine; diisopropanolamine; dipropyleneglycol; polypropylene glycol; 1,2-butanediol; 1,3-butanediol;1,4-butanediol; 2,3-butanediol; 2,3-dimethyl-2,3-butanediol;trimethylolpropane; cyclohexyldimethylol; triisopropanolamine;N,N,N′,N′-tetra-(2-hydroxypropyl)-ethylene diamine; diethylene glycolbis-(aminopropyl)ether; 1,5-pentanediol; 1,6-hexanediol;1,3-bis-(2-hydroxyethoxy)cyclohexane; 1,4-cyclohexyldimethylol;1,3-bis-[2-(2-hydroxyethoxy)ethoxy]cyclohexane;1,3-bis-{2-[2-(2-hydroxyethoxy)ethoxy]ethoxy}cyclohexane;trimethylolpropane; polytetramethylene ether glycol, preferably having amolecular weight from about 250 to about 3900; and mixtures thereof.

Additional materials, as known in the art, may be added to the polyureacompositions. These additional materials include, but are not limitedto, catalysts, wetting agents, coloring agents, optical brighteners,cross-linking agents, whitening agents such as titanium dioxide and zincoxide, ultraviolet (UV) light absorbers, hindered amine lightstabilizers, defoaming agents, processing aids, surfactants, and otherconventional additives. For example, wetting additives may be added tomore effectively disperse the pigments. Antioxidants, stabilizers,softening agents, plasticizers, including internal and externalplasticizers, impact modifiers, foaming agents, density-adjustingfillers, reinforcing materials, and compatibilizers also may be added tothe composition in amounts known in the art. Generally, the additiveswill be present in the composition in an amount between about 1 andabout 70 weight percent based on the total weight of the compositiondepending upon the desired properties.

A catalyst may also be employed to promote the reaction between theprepolymer and the curing agent to make the polyurea composition.Suitable catalysts include, but are not limited to bismuth catalyst;zinc octoate; stannous octoate; tin catalysts such as bis-butyltindilaurate, bis-butyltin diacetate, stannous octoate; tin (II) chloride,tin (IV) chloride, bis-butyltin dimethoxide,dimethyl-bis[1-oxonedecyl)oxy]stannane, di-n-octyltin bis-isooctylmercaptoacetate; amine catalysts such as triethylenediamine,triethylamine, and tributylamine; organic acids such as oleic acid andacetic acid; delayed catalysts; and mixtures thereof. The catalyst ispreferably added in an amount sufficient to catalyze the reaction of thecomponents in the reactive mixture. In one embodiment, the catalyst ispresent in an amount from about 0.001 percent to about 5 percent byweight of the composition.

Preferably, the polymer matrix constituting the ball covering is a purepolyurea composition. That is, the polymer composition contains onlyurea linkages having the following general structure:

However, as discussed above, it is recognized that a polyurea/urethanehybrid composition also may be prepared in accordance with thisinvention. This occurs if the polyurea prepolymer is cured withhydroxyl-terminated curing agents. Any excess isocyanate in the polyureaprepolymer reacts with the hydroxyl groups in the curing agent and formsurethane linkages. The resulting polyurea/polyurethane compositioncontains both urea linkages (as described above) and urethane linkageshaving the following general structure:

In one version of the ball covering, the polymer matrix constituting theball covering consists of 100% by weight of the polyurea composition ofthis invention. In another version, the polymer matrix of the ballcovering is a polyurea/polyurethane hybrid blend. The blend containsabout 10 to about 90% by weight of the polyurea composition and about90% to about 10% of a polyurethane composition. In yet anotherembodiment, the polymer matrix of the ball covering is a blend of about10 to about 90% by weight of the polyurea composition and about 90% toabout 10% of another polymer or other material such as vinyl resins,polyesters, polyamides, or polyolefins.

The polyurea cover materials of this invention may be used with any typeof ball construction known in the art. Such golf ball designs include,for example, two-piece, three-piece, and four-piece designs. The core,intermediate casing, and cover portions making up the golf ball each canbe single or multi-layered. Referring to FIG. 1, a single layered(two-piece) golf ball (10) having a solid core (12) and polyurea cover(14) of this invention is shown. FIG. 2 shows a multi-layered(three-piece) golf ball (20) that can be made in accordance with thisinvention. In this version, the ball (20) includes a solid core (22), anintermediate casing layer (24), and polyurea cover (26).

The core portions (12, 22) in the golf balls (10, 20) shown in FIGS. 1and 2, respectively are typically made from compositions containing abase rubber, filler, initiator agent, and cross-linking agent. The baserubber normally is a natural or synthetic rubber, such as polybutadienerubber. In one embodiment, the base rubber is 1,4-polybutadiene having acis-structure of at least 40%. The polybutadiene can be blended withother elastomers such as natural rubber, polyisoprene rubber,styrene-butadiene rubber and/or other polybutadienes. Another suitablerubber that may be used in the core is trans-polybutadiene. Thispolybutadiene isomer is formed by converting the cis-isomer of thepolybutadiene to the trans-isomer during a molding cycle. A soft andfast agent such as pentachlorothiophenol (PCTP) or ZnPCTP can be blendedwith the polybutadiene. These compounds may also function ascis-to-trans catalyst to convert some cis-1,4 bonds in the polybutadieneinto trans 1,4 bonds. Fillers, which may be used to modify suchproperties as the specific gravity (density-modifying materials),hardness, weight, modulus, resiliency, compression, and the like may beadded to the core composition. Normally, the fillers are inorganic, andsuitable fillers include numerous metals or metal oxides, such as zincoxide and tin oxide, as well as barium sulfate, zinc sulfate, calciumcarbonate, barium carbonate, clay, tungsten, tungsten carbide, silica,and mixtures thereof.

The intermediate layer (24), as shown in the golf ball (20) of FIG. 2,may be made of any suitable material known in the art includingthermoplastic and thermosetting materials. Suitable thermoplasticcompositions for forming the intermediate core layer include, but arenot limited to, partially- and fully-neutralized ionomers, graftcopolymers of ionomer and polyamide, and the following non-ionomericpolymers, including homopolymers and copolymers thereof, as well astheir derivatives that are compatibilized with at least one grafted orcopolymerized functional group, such as maleic anhydride, amine, epoxy,isocyanate, hydroxyl, sulfonate, phosphonate, and the like: polyesters;polyamides; polyamide-ethers, and polyamide-esters; polyurethanes,polyureas, and polyurethane-polyurea hybrids; fluoropolymers;non-ionomeric acid polymers, such as E/Y- and E/X/Y-type copolymers,wherein E is an olefin (e.g., ethylene), Y is a carboxylic acid, and Xis a softening comonomer such as vinyl esters of aliphatic carboxylicacids, and alkyl alkylacrylates; metallocene-catalyzed polymers;polystyrenes; polypropylenes and polyethylenes; polyvinyl chlorides andgrafted polyvinyl chlorides; polyvinyl acetates; polycarbonatesincluding polycarbonate/acrylonitrile-butadiene-styrene blends,polycarbonate/polyurethane blends, and polycarbonate/polyester blends;polyvinyl alcohols; polyethers; polyimides, polyetherketones,polyamideimides; and mixtures of any two or more of the abovethermoplastic polymers.

Examples of commercially available thermoplastics suitable for formingthe intermediate casing layer include, but are not limited to: Pebax®thermoplastic polyether block amides, commercially available from ArkemaInc.; Surlyn® ionomer resins, Hytrel® thermoplastic polyesterelastomers, and ionomeric materials sold under the trade names DuPont®HPF 1000 and HPF 2000, all of which are commercially available from E.I.du Pont de Nemours and Company; Iotek® ionomers, commercially availablefrom ExxonMobil Chemical Company; Amplify® IO ionomers of ethyleneacrylic acid copolymers, commercially available from The Dow ChemicalCompany; Clarix® ionomer resins, commercially available from A. SchulmanInc.; Elastollan® polyurethane-based thermoplastic elastomers,commercially available from BASF; and Xylex® polycarbonate/polyesterblends, commercially available from SABIC Innovative Plastics. Theadditives and filler materials described above may be added to theintermediate layer composition to modify such properties as the specificgravity (density-modifying materials), hardness, weight, modulus,resiliency, compression, and the like.

The ionomeric resins can be blended with non-ionic thermoplastic resins.Examples of suitable non-ionic thermoplastic resins include, but are notlimited to, polyurethane, poly-ether-ester, poly-amide-ether,polyether-urea, thermoplastic polyether block amides (e.g., Pebax® blockcopolymers, commercially available from Arkema Inc.),styrene-butadiene-styrene block copolymers,styrene(ethylene-butylene)-styrene block copolymers, polyamides,polyesters, polyolefins (e.g., polyethylene, polypropylene,ethylene-propylene copolymers, polyethylene-(meth)acrylate,polyethylene-(meth)acrylic acid, functionalized polymers with maleicanhydride grafting, Fusabond® functionalized polymers commerciallyavailable from E.I. du Pont de Nemours and Company, functionalizedpolymers with epoxidation, elastomers (e.g., ethylene propylene dienemonomer rubber, metallocene-catalyzed polyolefin) and ground powders ofthermoset elastomers.

Referring back to FIGS. 1 and 2, the core portions (12, 22) are shown assingle-piece structures made from a natural or synthetic rubbercomposition such as polybutadiene. In other instances, a multi-piececore may be constructed; that is, there may be two or more core portionsor layers. For example, in FIG. 3, a golf ball (28) having a two-piecesolid core (30, 32), intermediate layer (34), and a cover layer (36)made in accordance with this invention is shown. The intermediate layer(34) may be made of the above-described ionomer resins, and the covermay be made of the polyurea composition of this invention. Themulti-layered core (constituting inner and outer core layers (30, 32))may be referred to as the “center” of the ball. The inner core portion(30) may be made of a first base rubber material and the outer corelayer (32), which surrounds the inner core (30), may be made of a secondbase rubber material. The respective core pieces (30, 32) may be made ofthe same or different rubber materials as described above. Cross-linkingagents and fillers may be added to the rubber materials of each corepiece.

Golf balls made in accordance with this invention can be of any size,although the USGA requires that golf ball used in competition have adiameter of at least 1.68 inches and a weight of no greater than 1.62ounces. For play outside of USGA competition, the golf balls can havesmaller diameters and be heavier. Preferably, the diameter of the golfball is in the range of about 1.68 to about 1.80 inches. The coregenerally will have a diameter in the range of about 1.26 to about 1.60inches. In one preferred version, the single-piece core has a diameterof about 1.57 inches. The hardness of the core may vary depending uponthe desired properties of the ball. In general, core hardness is in therange of about 30 to about 65 Shore D and more preferably in the rangeof about 35 to about 60 Shore D. The compression of the core portion isgenerally in the range of about 70 to about 110 and more preferably inthe range of about 80 to about 100. As shown in FIGS. 1-3, the coreportions generally makes up a substantial portion of the ball, forexample, the core may constitute at least 95% or greater of the ballstructure.

Referring to FIGS. 2 and 3, which show golf balls having intermediatelayers (24, 34) respectively, the range of thicknesses for theintermediate layer can vary because different materials can be used. Ingeneral, however, the thickness of the intermediate layer will be in therange of about 0.015 to about 0.120 inches and preferably about 0.020 toabout 0.060 inches. Multiple intermediate layers may be disposed betweenthe inner core and outer cover. Preferably, the overall diameter of thecore and all intermediate layers is about 90 percent to about 98 percentof the overall diameter of the finished ball. As shown in FIGS. 1-3 anddescribed above, the cover material (14, 26, and 36) is made of thepolyurea composition of this invention. The polyurea cover provides theball with good mechanical strength and durability as well as playingperformance properties. The thickness of the polyurea cover may vary,but it is generally in the range of about 0.015 to about 0.090 inches,preferably about 0.020 to about 0.050 inches, and more preferably about0.020 inches to about 0.035 inches.

The golf balls of this invention may contain layers having the samehardness or different hardness values. Surface hardness and materialhardness are important properties considered in ball design andconstruction. The test methods for measuring surface hardness andmaterial hardness are described in further detail below. There can beuniform hardness throughout the different layers of the ball or therecan be hardness gradients across the layers. For example, the hardnessof the core may vary, but it is generally in the range of about 30 toabout 65 Shore D and more preferably in the range of about 35 to about60 Shore D. The intermediate layer(s) of the present invention may alsovary in hardness depending on the specific construction of the ball. Inone embodiment, the hardness of the intermediate layer is about 30 toabout 75 Shore D. Like the core and intermediate layers, the hardness ofthe cover may vary, but it is generally in the range of about 30 toabout 65 Shore D. In some instances, the core is intended to be softerthan the intermediate layers. For example, the core may have a hardnessin the range of about 40 to about 55 Shore D, and the intermediate layermay have a hardness in the range of about 60 to about 75 Shore D.Furthermore, in some instances, the outer cover layer is intended to besofter than the intermediate layer. Thus, if the intermediate layer hasa hardness in the range of about 60 to about 75 Shore D, the covermaterial may have a hardness of about 20 to about 55 Shore D.

The golf balls of this invention may be constructed using any suitabletechnique known in the art. These methods generally include compressionmolding, flip molding, injection molding, retractable pin injectionmolding, reaction injection molding (RIM), liquid injection molding(LIM), casting, vacuum forming, powder coating, flow coating, spincoating, dipping, spraying, and the like.

More particularly, the core of the golf ball may be formed usingcompression molding or injection molding. As discussed above, suitablecore materials include thermoset materials, such as, for example,rubber, styrene butadiene, polybutadiene, isoprene, polyisoprene,trans-isoprene, as well as thermoplastics such as, for example, ionomerresins, polyamides or polyesters. The intermediate casing layer, whichmay be made of ionomer resins or other polymer materials, may be formedusing known methods such as, for example, retractable pin injectionmolding or compression molding.

This intermediate casing layer is then covered with a cover layer usingeither reaction injection molding or a casting process. In a castingprocess, the polyurea mixture is dispensed into the cavity of an uppermold member. This first mold half has a hemispherical structure. Then,the cavity of a corresponding lower mold member is filled with thepolyurea mixture. This second mold half also has a hemisphericalstructure. The cavities are typically heated beforehand. A ball cupholds the golf ball (core and overlying casing layer) under vacuum.After the polyurea mixture in the first mold half has reached asemi-gelled or gelled sate, the pressure is removed and the golf ball islowered into the upper mold half containing the polyurea mixture. Then,the first mold half is inverted and mated with the second mold halfcontaining polyurea mixture which also has reached a semi-gelled orgelled state. The polyurea mixtures, contained in the mold members thatare mated together, form the golf ball cover. The mated first and secondmold halves containing the polyurea mixture and golf ball center may benext heated so that the mixture cures and hardens. Then, the golf ballis removed from the mold. The ball may be heated and cooled as needed.

The ball cover materials made with the polyurea compositions of thisinvention have several advantageous properties and benefits includingthe following. First, the cover materials show good moisture resistance.While not wishing to be bound by any theory, it is believed thehydrophobic backbone of the amine-terminated polycaprolactones used toproduce the polyurea composition, as described above, significantlycontributes to this enhanced moisture resistance. Secondly, the polyureacover materials have high durability and abrasion resistance. Thepolyurea cover materials maintain their original appearance andaesthetics over time.

Test Methods

Hardness: The surface hardness of a golf ball layer (or other sphericalsurface) is obtained from the average of a number of measurements takenfrom opposing hemispheres, taking care to avoid making measurements onthe parting line of the core or on surface defects such as holes orprotrusions. Hardness measurements are made pursuant to ASTM D-2240“Indentation Hardness of Rubber and Plastic by Means of a Durometer.”Because of the curved surface of the golf ball layer, care must be takento ensure that the golf ball or golf ball subassembly is centered underthe durometer indentor before a surface hardness reading is obtained. Acalibrated digital durometer, capable of reading to 0.1 hardness units,is used for all hardness measurements and is set to take hardnessreadings at 1 second after the maximum reading is obtained. The digitaldurometer must be attached to and its foot made parallel to the base ofan automatic stand. The weight on the durometer and attack rate conformsto ASTM D-2240. It should be understood that there is a fundamentaldifference between “material hardness” and “hardness as measureddirectly on a golf ball.” For purposes of the present invention,material hardness is measured according to ASTM D2240 and generallyinvolves measuring the hardness of a flat “slab” or “button” formed ofthe material. Surface hardness as measured directly on a golf ball (orother spherical surface) typically results in a different hardnessvalue. The difference in “surface hardness” and “material hardness”values is due to several factors including, but not limited to, ballconstruction (that is, core type, number of cores and/or cover layers,and the like); ball (or sphere) diameter; and the material compositionof adjacent layers. It also should be understood that the twomeasurement techniques are not linearly related and, therefore, onehardness value cannot easily be correlated to the other.

It is understood that the golf balls having a polyurea cover describedand illustrated herein represent only presently preferred embodiments ofthe invention. It is appreciated by those skilled in the art thatvarious changes and additions can be made to such golf balls withoutdeparting from the spirit and scope of this invention. It is intendedthat all such embodiments be covered by the appended claims.

1. A golf ball, comprising: a core; and a polyurea cover materialproduced by a reaction of ingredients comprising isocyanate,amine-terminated polycaprolactone, and amine-terminated cross-linkingagent.
 2. The golf ball of claim 1, wherein the core comprisespolybutadiene.
 3. The golf ball of claim 1, wherein the isocyanate isselected from the group consisting of MDI, H₁₂MDI, PPDI, TDI, IPDI, HDI,NDI, XDI, TMXDI, THDI, and TMDI, and homopolymers and copolymers andmixtures thereof.
 4. The golf ball of claim 1, wherein the curing agentis an amine-terminated curing agent selected from the group consistingof 4,4′-diamino-diphenylmethane; 3,5-diethyl-(2,4- or 2,6-)toluenediamine; 3,5-dimethylthio-(2,4- or 2,6-)toluenediamine;3,5-diethylthio-(2,4- or 2,6-) toluenediamine:2,2′-dichloro-3,3′,5,5′-tetraethyl-4,4′-diamino-diphenylmethane;polytetramethyleneglycol-di(p-aminobenzoate);4,4′-bis(sec-butylamino)-dicyclohexylmethane; and mixtures thereof. 5.The golf ball of claim 1, wherein the polyurea cover material furthercomprises pigments and fillers.
 6. The golf ball of claim 1, wherein thecore has a diameter of about 1.26 to about 1.60 inches.
 7. The golf ballof claim 1, wherein the cover has a thickness of about 0.015 to about0.090 inches.
 8. The golf ball of claim 7, wherein the cover has athickness of about 0.020 to about 0.050 inches.
 9. The golf ball ofclaim 8, wherein the cover has a thickness of about 0.020 to about 0.035inches.
 10. The golf ball of claim 1, wherein the core has a hardness inthe range of about 30 to about 65 Shore D.
 11. The golf ball of claim 1,wherein the cover has a material hardness of about 30 to about 65 ShoreD.
 12. The golf ball of claim 11, wherein the cover has a materialhardness of about 35 to about 55 Shore D.
 13. A golf ball, comprising: acore; an intermediate casing layer overlying the core; and a polyureacover material produced by a reaction of ingredients comprisingisocyanate, amine-terminated polycaprolactone, and amine-terminatedcross-linking agent, the cover material overlying the casing layer. 14.The golf ball of claim 13, wherein the core comprises polybutadiene. 15.The golf ball of claim 13, wherein the casing layer comprises ionomericresin.
 16. The golf ball of claim 13, wherein the casing layer comprisesa blend of ionomeric resin and non-ionomeric resin.
 17. The golf ball ofclaim 13, wherein the isocyanate is selected from the group consistingof MDI, H₁₂MDI, PPDI, TDI, IPDI, HDI, NDI, XDI, TMXDI, THDI, and TMDI,and homopolymers and copolymers and mixtures thereof.
 18. The golf ballof claim 13, wherein the curing agent is an amine-terminated curingagent selected from the group consisting of4,4′-diamino-diphenylmethane; 3,5-diethyl-(2,4- or 2,6-) toluenediamine;3,5-dimethylthio-(2,4- or 2,6-)toluenediamine; 3,5-diethylthio-(2,4- or2,6-) toluenediamine:2,2′-dichloro-3,3′,5,5′-tetraethyl-4,4′-diamino-diphenylmethane;polytetramethyleneglycol-di(p-aminobenzoate);4,4′-bis(sec-butylamino)-dicyclohexylmethane; and mixtures thereof. 19.The golf ball of claim 13, wherein the polyurea cover material furthercomprises pigments and fillers.
 20. The golf ball of claim 13, whereinthe core has a diameter of about 1.26 to about 1.60 inches.
 21. The golfball of claim 13, wherein the intermediate casing layer has a thicknessof about 0.015 to about 0.120 inches.
 22. The golf ball of claim 21,wherein the intermediate casing layer has a thickness of about 0.020 toabout 0.060 inches.
 23. The golf ball of claim 13, wherein the cover hasa thickness of about 0.015 to about 0.090 inches.
 24. The golf ball ofclaim 23, wherein the cover has a thickness of about 0.020 to about0.050 inches.
 25. The golf ball of claim 23, wherein the cover has athickness of about 0.020 to about 0.035 inches.